terials closely resembling vertebrate-type peptide hormones (insulin, matostatin, ACTH, relaxin, calcitonin, arginine-vasotocin) have been entified in unicellular organisms. These studies were extended to include search for similar peptides in plants. Insulin and somatostatin-related terials were found in extracts of spinach, lemna and rye. Purification of ptides was achieved using gel chromatography and high performance liquid romatography and activity demonstrated by the specific hormone dioimmunoassays and bioassays. ing recombinant DNA technology, the genes encoding for insulin and matostatin were searched for in genomic extract from unicellular eukaryotes d prokaryotes. Specific DNA sequences were found which hybridized to cDNA obes for rat somatostatin and rat insulin and are currently being analyzed r sequence composition. These results suggest that hormone-like peptides e evolutionarily very old.